By: Chris Alderman, Michelle Strathy, Katrina Cofield, and Stuart Edwards
Protistans are eukaryotes. They have a nucleus, large ribosomes, mitochondria, endoplasmic reticulum, and golgi bodies. Many species have chloroplasts. Some protists divide by way of mitosis, meiosis, or both. The majority of protistians are single-celled, but nearly every lineage also has multicelled forms. Protists are important for the use of food. Saprobes resemble some bacteria and fungi, and some predators and parasites resembles animals. Some are heterotrophs and some are autotrophs. Chytrids, water molds, slime molds, protozans, and sporozans are heterotrophs.
Evolution of the Protista Kingdom
Early life on Earth
Evolved from bacteria
Represent intermediate step in evolution of Three Kingdoms
Knowing the Protista
Defining the Protista
Diverse species, ranging from single cells to giant kelps, that are photoautotrophs, heterotrophs, or both
Protists can be heterotrophic or autotrophic
Heterotrophic cannot make their own food
Autotrophic can survive by making their own food
Protists are mostly unicellular (except for multicellular algae)
Other protists are all unicellular heterotrophic eukaryotes (except for Fungi)
Prokaryotic vs. Eukaryotic
First evolved cells were the prokaryotic
Prokaryotic cells do not have a nucleus
Eukaryotic cells do have a true nuclei
Eukaryotic cells were first protistans
Eukaryotic cells have membrane-enclosed organelles
Eukaryotic cells have flagella and cilia
Eukaryotic cell Development
Endosymbiotic model of Eukaryotic cell evolution
3.8 billion years ago archaebacteria and eukaryotic cells diverged from the lineage that led to modern eubacteria
Oxygen-releasing photosynthetic bacteria evolved
Later, oxygenized atmosphere ended further spontaneous chemical evolution of life
This atmosphere was a key selection pressure in the evolution of eukaryotic cells
Three Types of Protists
The Protist Kingdom is known as the "catch all" Kingdom; they are the organisms that donít really fit in with any other Kingdom. Since there are such a wide variety of protists they are arranged into three groups. The three groups are arranged depending on whether they have animal-like characteristics, fungus-like characteristics, or plant-like characteristics. Therefore the three groups of protists are: Animal-like protists, Fungus-like protists, and Plant-like protists.
http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookDiversity_3.html Contains the evolution of the protist along with the classification. Also has many great diagrams and pictures.
http://megasun.bch.umontreal.ca/protists/protists.html Contains links to pictures and other resourses available.
http://www.pburg.k12.nj.us/phs/biopages/protista8/cells.htm Contains pictures and brief descriptions of different types of protists.
http://www.sp.uconn.edu/~bi102vc/102f99/terry/protists.html A teachers outline of a lecture about Protists.
http://people.mw.mediaone.net/maxhalp/protista.html Contains examples of Protists and brief descriptions for each.
Animal-like protists are called protozoans ("first animals") because it is thought that they are the evolutionary history of animals. They share many common traits with animals. All of the animal-like protists are heterotrophs; they are unable to make their own food. But unlike animals, they are unicellular. Since they cant make their own food they must be able to move through their environment and catch their food.
The animal-like protists are divided into four groups based upon their means of mobility and manners for catching their food. They are divided into: protists with pseudopods, protists with cilia, protists with flagella, and parasitic protists.
http://www.cbu.edu/~seisen/ProtistsI.htm Contains a chart on animal-like protests with a few links.
http://www.knossos.org/knossids2001/protistpage.html Contains a wonderful chart about animal-like protests. It includes pictures and more links.
http://pc38.ve.weber.k12.ut.us/Reese/animal_like.htm Contains pictures of some animal-like protists.
Protists with Pseudopods
A pseudopod is a "false foot" that slowly moves the protist. These protists move towards their food or prey by extending their cytoplasm into a "false foot". The "false foot" extends from the cytoplasm, attaches to the ground, and pulls the rest of the body toward the food. The pseudopods are not only for the means of locomotion; they also capture the food. They capture the food by wrapping the "false foot" around the prey and bringing it into their bodies. One example of an animal-like protist with pseudopods is the Amoeba (see picture above).
Amoebas are single celled animal-like protists that live in moist soil, freshwater, and salt water. There are different types of Amoeba but they all use pseudopods as means of locomotion and capturing food. Most of the Amoebas are free-living and eat things like other protozoans and bacteria; few Amoebas are parasitic and live on or in other organisms, where they obtain nutrients.
An example of an Amoeba is Entamueba histolytica. This Amoeba is the cause of amoebic dysentery, which is a deadly infectious disease found mostly in tropical areas and usually in areas where sanitation is poor. This disease is the leading cause of death for infants and toddlers; their immune systems are not yet developed, therefore they cannot destroy the disease.
Below is the life cycle of Entamoeba hisolytica.
http://more.abcnews.go.com/sections/living/dailynews/amoeba010421.html About an Amoeba that killed a three-year-old girl.
Protists with Cilia
Cilia are tiny hair-like structures that surround some protists. The cilia beat back and forth. This movement enables the animal-like protist to move through its aquatic environment. The cilia also help the organism capture food. When the cilia beat, the prey (food) is moved into its body.
Cilia are composed of ten pairs of microtubules. The microtubules are arranged in what is known as the 9+2 configuration. Of the ten pairs of microtubules nine pairs form a circle. Inside the circle lies the tenth pair; this is how it got the name 9+2 configuration.
One example of an animal-like protist with cilia is the Paramecium.
http://www.cytochemistry.net/Cell-biology/cilia.htm Contains information about what cilia are made of, how they move, and how they capture food.
Paramecium is one known ciliated protist. The cilia help the Paramecium push the food and water into the cell body. The food then becomes enclosed in a vesicle filled with enzymes. In this vesicle the enzymes help the organism to digest the food.
The cilia can also helps the protist move towards the food/prey by beating the organism through the aquatic environment. The cilia can become leg-like structures under the Paramecium allowing it to "run."
http://www.pbrc.hawaii.edu/membio/paramecium/ A conference about Paramecium.
Protists with Flagella
Flagella are long whip-like structures that move back and forth allowing the animal-like protist to move. Protists with flagella beat the long whip-like structure to move through their aquatic environments. These organisms can be free-living; some are parasitic, living in moist tissues of plants and animals. Sometimes the parasitic protists help their host, but others are harmful.
Flagella, like cilia, are composed of microtubules. They are arranged in a 9+2 configuration. Nine of the pairs of microtubules form a circle around the tenth pair.
One example of an animal-like protist with flagella is Giardia lamblia.
http://www.cytochemistry.net/Cell-biology/cilia.htm Contains information about what flagella are made of, how they move, and how they capture food.
Giardia lamblia is an animal-like protist that uses flagella as its means of locomotion and food capturing. It is an internal parasite the causes diarrhea. Giardia lamblia contaminates waters of aquatic lands and river banks. When animals and humans drink the water, the protist becomes parasitic to the host. It leaves the host through the feces. After it has left the host it then contaminates everything that comes into contact with the feces. Many humans get this disease by drinking infected waters or eating infected meats.
Below is the life cycle of Giardia Lamblia.
http://www.comeunity.com/adoption/health/parasites/giardiasis.html An article about children in orphanages and Giardia lamblia.
http://more.abcnews.go.com/sections/travel/tactics/drinkwater.html An ABC News report about to protect yourself from Giardia Lamblia.
The parasitic protists are animal-like protists that live in or on another organism, obtaining all its nutrients from that host organism. Many of these protists are disease causing. These protists go in and out of the active stage and the dormant stage. When conditions are good for them they are active; when conditions are bad they become dormant. One example of this parasitic animal-like protist is Plasmodium, which causes malaria.
Plasmodium is a parasitic animal-like protist. It is the cause of malaria. Plasmodium is transported through mosquitoes. While in the mosquito the Plasmodium is in a dormant stage. When it is transported into the human it becomes active. It is mostly found in the red blood cells of humans. The Plasmodium asexually reproduces inside the liver and then enters the red blood cells. The red blood cells are destroyed in massive amounts. Merozoites are produced in some of the red blood cells. These merozoites develop into the male and female gametophytes. The infected gametophytes are taken in through a mosquito and the process begins all over again.
Below is the life cycle of Plasmodium.
http://www-micro.msb.le.ac.uk/224/Malaria.html An article about Malaria. Where it is found, the life cycle, and how it is transported.
http://more.abcnews.go.com/sections/science/DyeHard/dyehard000601.html An ABC News coverage about Malaria.
Fungus-like protists are heterotrophic, they cannot make their own food, and thus they must be able to move at some point in their lives. These protists contain long hyphae-like strands thus they contain the physical appearance of fungi. The difference lies in that the hyphae of fungi are white while the hyphae of protists are usually bright in color.
The fungus-like protists can act as decomposers. They break down dead organisms by releasing digestive enzymes into the dead organism. In the end materials useful to other living organisms are released into the surrounding environment.
Two examples of the fungus-like protists are water molds and slime molds.
Water molds are fungus-like protists that live in moist environments. They look like tiny threads with a hazy covering (when in a damp environment). Most water molds are decomposers, breaking down dead organisms; few water molds are parasites, living in or on other organisms.
Water molds attack foods such as potatoes, cabbage, and corn. They are capable of completely destroying crops. An example of the devastation a water mold is capable of doing happened between the years of 1845 and 1860. The growing seasons at this time was a cold and damp one; these are conditions that encourage the spread of the water mold Phytophthora infestans. This water mold is the cause of rotting potato plants (late blight). It infested all of the potato crops in Ireland. During this period one third of Irelands population died; they either starved to death or were killed by the infested potatoes.
http://www.ucmp.berkeley.edu/chromista/oomycota.html Contains information about the water mold Oomycota and its role in the environment.
Slime molds are a fungus-like protist that lives in moist soil, decaying plants, and trees. They have a very bright appearance.
Slime molds are single celled organisms. When conditions become unfavorable the single celled organisms join together and act like a "multi-cellular" organism. The protists will then form a sporangia-a cluster of cells on top of a stalk. The sporangia consist of living cells in a dormant stage, while the stalk consists of dead cells that act as a foot and push the cells to favorable conditions. When conditions become favorable the "multi-cellular" organism separates itself back into the single celled organisms.
http://www.sharnoff.com/myxos1.html Some really neat pictures of Slime Molds.
Plant-like protists are autotrophic; they can make their own foods. They live in soil, on the barks of trees, in fresh water, and in salt water. Plant-like protists are very important to the earth because they produce an abundant amount of oxygen. They are the basis for the aquatic food chain.
These protists are similar to plants. Most are photosynthetic. Some have stem-like structures called stipes and anchoring structures called holdfasts, while plants have actual stems and roots. Many of these protists release their eggs into the environment where the sperm will fertilize the egg. Plants on the other hand will retain the egg in the "parent" plant where it will fertilize.
Some examples of plant-like protists are: Euglenoids, Dinoflagellates, Chrysophytes, Green Algae, Red Algae, and Brown Algae.
http://www.personal.psu.edu/users/t/j/tjk153/ Contains information and charts about plant-like protests, has links to different types of plant-like protists.
Euglenoids are plant-like protists that are usually found in fresh water. During the day these protists are autotrophic; they can make their own foods. When night falls they become heterotrophic; they are unable to make their own foods, and thus they must be able to find it. Some Euglenoids have flagella to help them move during the heterotrophic stage.
The Eugleoid is a single celled organism with an abundance of organelles. They have an "eye spot" which covers a light-sensitive receptor. The cell will move to places where the light suits it best.
http://euglenoid.hihome.com/ Provides information and answers questions about Euglenoids.
Dinoflagellates are plant-like protists found in salt water. They are unicellular and have flagella to help them move through the water. The Dinoflagellates are capable of glowing in the dark. They are the cause of Red Tide, when there is an outburst in population and in turn water becomes red/brown in color.
The Dinoflagellates can produce toxins. If a human eats seafood contaminated with the toxins he/she will have memory loss and other impaired brain functions.
One dinoflagellate that has gotten out of control is Pfiesteria. Pfiesteria grows in fertilizer and raw sewage. It has killed a billion fish along the costs of North Carolina, Maryland, and Virginia since 1991.
http://www.microscopy-uk.org.uk/mag/art97b/hell.html An article talking about Pfiesteria piscicida.
http://www.acnatsci.org/erd/ea/pfiester.html An article about the possible connection between Pfiesteria and pollution.
http://more.abcnews.go.com/sections/science/dailynews/coastpollution000405.html An ABC News coverage about the damage of a Red Tide.
Chrysophytes are plant-like protists found in toothpaste, scouring products, and filters. Chrysophytes have a glasslike cell wall. The Chrysophytes are free-living, photosynthetic, unicellular protists. They consist of diatoms, golden algae, and yellow-green algae. Many Chrysophytes form colonies.
The diatoms are photosynthetic. They contain a shell that is made of silica. The cell has two parts that overlap. Over millions of years the shells become crushed and form the sand found on the bottom of oceans and lakes.
Golden algae have no cell wall. They do have scales made of silica. They also contain chloroplast and they do photosynthesize.
Yellow-green algae also have no cell wall. They are unable to move, but some do have flagella to help assist movement when conditions become harsh. This algae is common in nearly all aquatic environments.
http://www.ucmp.berkeley.edu/chromista/chrysophyta.html A brief description of Chrysophyta.
Green algae are plant-like protists that are structurally closest to plants. The green algae can be seen in many forms. Most are unicellular, some live in colonies, and few are milticellular. Green algae grows at the surface of the ocean, in marine waters, below the surface of the soil, and in rocks, tree bark, in other organisms, and in snow.
Red algae is a plant-like protist that can be found in aquatic areas; most live in marine waters, but some are found in fresh waters as well. Not all red algae appear red. The color depends on the pigmentation and chlorophyll abundance in the protist. They can appear green, purple, and black. The cell walls of red algae are composed of agar, which gives it a slimy/slippery feeling.
Humans use red algae every day. The red algae Eucheuma is used as thickening agents in such things as paints, dairy products, and hair conditioners.
Brown algae is a plant-like protist found in cool temperature marine waters. They range in colors from dark brown to golden, depending on the amount and arrangement of certain pigments. They range in size from thirty meters, such as giant kelp, to microscopic organisms.
Macrocyctis is giant kelp. It is one of the most complex of all protistans. They are multicellualr and contain stipes (stem-like structures), blades (leaf-like structures), and holdfasts (anchoring structures). Kelp often live in giant colonies, creating a kelp bed. These giant kelp beds act like underwater "forests". Many fish, bacteria, and other protistans live their lives with in the giant kelp "forests."
Brown algae are found in many products such as: ice cream, pudding, jelly beans, salad dressing, canned foods, frozen foods, beer, cough syrup, toothpaste, floor polish, cosmetics, and paper. Many people harvest kelp for food, mineral salt, and fertilizer for crops.
http://life.bio.sunysb.edu/marinebio/kelpforest.html Wonderful pictures of the enormous Kelp.
http://www.msnbc.com/local/knsd/nbcjh0oempc.asp An NBC News coverage about Kelp in San Diego, CA.
Alesse, P. 2001. http://www.knossos.org/knossids2001/protistpage.html
Callan, R. Hess, S. Seibel, N. & Wozniak, M. http://www.pburg.k12.nj.us/phs/biopages/protista8/cells.htm
Carl. 2000. http://lanesville.k12.in.us/LCSYellowpages/Tickit/Carl/protists.html
Chiang Mai University. 2001. http://www.medicine.cmu.ac.th/dept/parasite/official/deptpage.htm
Farabee, M.J. 2001. http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookDiversity_3.html
Harper, L. http://www.micscape.simplenet.com/mag/wimsmall/cilidr.html
Hidden Forest Designs. 2001. http://www.hiddenforest.co.nz/slime/index.htm
Ohio State University. 2001. http://www.biosci.ohio-state.edu/~parasite/home.html
Pearson, E. 2000. http://www.scienceman.com/scienceinaction/techidea_5.htm
Pennsylvania State University. 2001. http://www.personal.psu.edu/users/r/s/rsb151/bio110h/oom.html
Pleasanton Unified School District. 2001. http://www.pleasanton.k12.ca.us/AMADOR/Creek/field/protista/vorticel.html\
Starr, C. 2000. Biology Concepts and Applications. Brooks/Cole, Thomas Learning: United States.
Sweets, R.P. 1998. http://www.indiana.edu/~diatom/diatom.html
Terry, T.M. 1999. http://www.redtide.whoi.edu/hab/rtphotos/noctiluca.jpg
University Corporation for Atmospheric Research . 2001. www.windows.ucar.edu
University of California Museum of Paleontology, Berkeley. 2001. http://www.ucmp.berkeley.edu/chromista/oomycota.html
University of California Museum of Paleontology, Berkeley. 2001. http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html
University of California Museum of Paleontology, Berkeley. 2001. http://www.ucmp.berkeley.edu/protista/ciliata.html